526 research outputs found
Pb(Mg1/3Nb2/3)O3 (PMN) Relaxor: Dipole Glass or Nano-Domain Ferroelectric?
Combining our comprehensive investigations of polarization evolution,
soft-mode by Raman scattering and microstructure by TEM, and the results
reported in the literatures, we show that prototypical relaxor Pb(Mg1/3Nb2/3)O3
(PMN) is essentially ferroelectric for T<Tc~225 K. Its anomalous dielectric
behavior over a broad temperature range results from the reorientation of
domains in the crystal. A physic picture of the structure evolution in relaxor
is also revealed. It is found that nanometric ferroelectric domains (gennerally
called as polar nano-region (PNR)) interact cooperatively to form micrometric
domain. Such multiscale inhomogeneities of domain structure in addition to the
well-known inhomogeneities of chemical composition and local symmetry are
considered to play a crucial role in producing the enigmatic phenomena in
relaxor system.Comment: 16 pages, 10 figures;
http://www.intechopen.com/books/advances-in-ferroelectrics/pb-mg1-3nb2-3-o3-pmn-relaxor-dipole-glass-or-nano-domain-ferroelectric
First-principles calculations of lattice dynamics in CdTiO3 and CaTiO3: Phase stability and ferroelectricity
First-principles calculations of various phases of CdTiO3 carried out with the aim of obtaining insights into the mechanism of the ferroelectric phase transition and the structure of the low-temperature ferroelectric phase are reported. The results indicate that the preferred symmetry of the low-temperature phase is Pna2_1, rather than P21ma, corresponding to a small relative shift of the Ti and O ions in the paraelectric Pnma phase with the polarization axis parallel to the long axis. Calculated phonon dispersion curves show a distinct soft mode at the Γ point of the Pnma phase, which vanishes in the Pna2_1 phase, confirming that the transition to the ferroelectric phase is of the soft-mode displacive type. Calculations of perovskite CaTiO3, which also has an orthorhombic Pnma structure at room temperature but, unlike CdTiO3, does not exhibit a ferroelectric phase transition down to 4.2 K, were also carried out to help characterize the factors controlling ferroelectric phase transitions in perovskite titanates
Substellar Companions to Seven Evolved Intermediate-Mass Stars
We report the detections of substellar companions orbiting around seven
evolved intermediate-mass stars from precise Doppler measurements at Okayama
Astrophysical Observatory. o UMa (G4 II-III) is a giant with a mass of 3.1
M_sun and hosts a planet with minimum mass of m_2sini=4.1 M_J in an orbit with
a period P=1630 d and an eccentricity e=0.13. This is the first planet
candidate (< 13 M_J) ever discovered around stars more massive than 3 M_sun. o
CrB (K0 III) is a 2.1 M_sun giant and has a planet of m_2sini=1.5 M_J in a
187.8 d orbit with e=0.19. This is one of the least massive planets ever
discovered around ~2 M_sun stars. HD 5608 (K0 IV) is an 1.6 M_sun subgiant
hosting a planet of m_2sini=1.4 M_J in a 793 d orbit with e=0.19. The star also
exhibits a linear velocity trend suggesting the existence of an outer, more
massive companion. 75 Cet (G3 III:) is a 2.5 M_sun giant hosting a planet of
m_2sini=3.0 M_J in a 692 d orbit with e=0.12. The star also shows possible
additional periodicity of about 200 d and 1880 d with velocity amplitude of
~7--10 m/s, although these are not significant at this stage. nu Oph (K0 III)
is a 3.0 M_sun giant and has two brown-dwarf companions of m_2sini= 24 M_J and
27 M_J, in orbits with P=530.3 d and 3190 d, and e=0.126 and 0.17,
respectively, which were independently announced by Quirrenbach et al. (2011).
The ratio of the periods is close to 1:6, suggesting that the companions are in
mean motion resonance. We also independently confirmed planets around k CrB (K0
III-IV) and HD 210702 (K1 IV), which had been announced by Johnson et al.
(2008) and Johnson et al. (2007a), respectively. All of the orbital parameters
we obtained are consistent with the previous results.Comment: 21 pages, 14 figures, accepted for publication in PAS
Factors Relating to Coagulation, Fibrinolysis and Hepatic Damage After Liver Resection
A survey of the blood of twenty-two patients who had undergone hepatic resection was performed.
Serum levels of α-2 plasmin inhibitor-plasmin complex initially decreased from 1.58 ± 0.31 μg/ml on the preoperative day (PREOP), to 0.92 ± 0.14 μ/ml on the first postoperative day (POD 1), and then increased to 3.13 ± 0.92 μg/ml on the seventh postoperative day (POD 7) (mean ± SE)). Thrombin-anti-thrombin III complex (14.2 ± 4.3 ng/ml on PREOP and 26.0 ± 4.1 ng/ml on POD 7
(mean ± SE)) and D-dimer (335 ± 96 ng/ml on PREOP and 1859 ± 258 ng/ml on POD 7 (mean ±
SE)) increased in the early postoperative stage. The level of 6-keto-prostaglandin F1α increased after
the operations (from 13.2 ± 1.8 pg/ml on PREOP to 37.8 ± 12.8 pg/ml on POD 7 (mean ± SE)). The
level of thromboxane B-2 decreased at first, and then gradually increased and returned to its
preoperative level on POD 7 (144.7 ± 43.8 pg/ml on PREOP, 57.6 ± 27.5 pg/ml on POD1 and 152.5
± 58.4 pg/ml on POD 7 (mean ± SE)). Superoxide dismutase activity increased at first, and then
gradually decreased, postoperatively (2.8 ± 0.5 NU/ml on PREOP, 4.8 ± 0.8 NU/ml on POD1 and 2.6
± 0.3 NU/ml on POD 7 (mean ± SE)). That is, biodefensive reactions which protect patients against
the shift to disseminated intravascular coagulation (DIC) were inferred with by the increase in antiplatelet
aggregation, despite the activation of coagulation and fibrinolytic mechanisms after hepatic
resection
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